People usually rehome them between 6 and 8 weeks old. Some keep them a bit longer until about 10 weeks, but generally I find them more than ready at 8 weeks. The only problem with waiting longer is you have to start separating the boys and girls.
Josh, that's good. Here's just 1 link of many that explains why they need to stay with the doe for as long as possible. Rabbits systems are unlike any other and need special care and considerations.
"...If younger than eight weeks, and no longer with his mother, his runny stool problem may be due to his being weaned too young. Many pet stores will (illegally) sell rabbits younger than eight weeks of age (some as young as four weeks), because that is when they are still "cute" and more apt to be purchased on a whim. Sadly, many of these babies are doomed to succumb to intestinal disorders.
Unlike most mammals, baby rabbits have a sterile lower intestine until they begin to eat solid food at the age of 3-4 weeks. It is during this time that their intestines are at their most vulnerable: the babies need their mother's milk, which changes pH and provides vital antibodies that help the baby gradually adjust to his changing intestinal environment, to protect them against newly introduced microorganisms. Without mother's milk, a baby starting to eat solid food is highly susceptible to bacterial enteritis (inflammation of the intestinal lining), which can cause fatal diarrhea. Runny stool in a baby rabbit should be considered a life-threatening emergency..."